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Title: CARBON DIOXIDE AND TEMPERATURE EFFECTS ON FORAGE CROPS: II. TISSUE COMPOSITION AND NUTRITIVE VALUE.

Author
item FRITSCHI, F. - UNIV. OF FLORIDA
item BOOTE, K. - UNIV. OF FLORIDA
item SOLLENBERGER, L. - UNIV. OF FLORIDA
item Allen Jr, Leon

Submitted to: Global Change Biology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/6/1999
Publication Date: N/A
Citation: N/A

Interpretive Summary: Atmospheric carbon dioxide (CO2) concentrations have increased from 280 to 365 ppm since 1800, with the most rapid rise during the last 50 years. Global warming of 1.5 to 4.5 degrees Celsius (about 3 to 8 degrees Fahrenheit) is expected when and if CO2 increases to 700 ppm. Scientists at USDA, Agricultural Research Service in Gainesville, FL, studied the effect of doubled CO2 and higher temperatures on leaf tissue composition and nutritive value of forages, perennial peanut and bahiagrass, because little work has been done on these types of plants compared to annual crops. Elevated CO2 increased carbohydrates in perennial peanut leaves by almost 50 percent, but decreased leaf nitrogen (or protein) by 6 percent. There were no effects of CO2 on bahiagrass. The quality of the leaves of neither material was affected by temperature. Thus the total yield advantage of perennial peanut under high CO2 was partly offset by a decrease in nutritive value.

Technical Abstract: Atmospheric CO2 concentration and temperature are likely to increase in the future. Rhizoma peanut (Arachis glabrata Benth.), a C3 species, and bahiagrass (paspalum notatum Flugge), a C4 species, were grown in field soil in temperature-gradient greenhouses (TGGs) to evaluate the effects of CO2 and temperature on tissue composition and digestibility. Carbon dioxide levels were maintained at 365 (ambient) and 640 ppm. The TGGs were regulated to obtain air temperature sectors of 0.0, 1.5, 3.0, and 4.5 degrees Celsius above ambient. Elevated CO2 increased total non- structural carbohydrate (TNC) in rhizoma peanut leaves by 50 percent. Rhizoma peanut leaf N was 6 percent lower at elevated than ambient CO2. No effects of CO2 concentration and temperature were found on neutral detergent fiber (NDF) in rhizoma peanut leaves. Elevated CO2 increased NDF in bahiagrass leaves. Rhizoma peanut in vitro organic matter digestion (IVOMD) was higher at ambient (623 g kg-1) than at elevated CO2 (609 g kg-1) at the end of the season. However, no effects on the IVOMD were found during the season for rhizoma peanut or bahiagrass. In summary, elevated CO2 concentration had a greater negative effect on tissue composition of rhizoma peanut than of bahiagrass.